# MicroRNAs --- **MicroRNAs** are, as the name sugests, small [[RNA|RNAs]] that help...do something like degrade RNAs, I think. Regulation of mRNA stability is partly controlled by small RNAs called microRNAs microRNAs are sythesized from the same gene that is being regulated, but in an unusual fashion to create small hairpin loops that are trimmed into 22 nucleotide segments. An enzyme just cuts the little loop off which leaves a double-stranded RNA, which is quite uncommon in biology. The double stranded miRNAs are then denatured by RISC protein, and the resulting single stranded segments are used to located and destroy the full length mRNAs. RISC knows which strand is non-coding, and uses the non-coding strand to bind to the coding strand of mRNA and cause it to be degraded. It's a shutoff mechanism after the mRNAs have already been made. The sequences for the microRNAs are found outside the genes themselves. This is also really important: they are made up of a coding sequence and a non-coding sequence. How did two sequences from both sides of the DNA end up on one strand of RNA? And how does that match up with a different mRNA that is located somewhere else in the genome? We're making one strand that represents both strands that And the RISC complex knows which one is which. Apparently ___